Thus far our interest in heat-resistance has uncovered secrets of no very great practical value, however entertaining the uses to which we have seen them put. But not all the investigation of these principles has been dictated by considerations of curiosity and entertainment. As long ago as 1829, for instance, an English newspaper printed the following: Proof against Fire--On Tuesday week an experiment was made in presence of a Committee of the Academy of Sciences at Paris, by M. Aldini, for the purpose of showing that he can secure the body against the action of flames so as to enable firemen to carry on their operations with safety. His experiment is stated to have given satisfaction. The pompiers were clothed in asbestos, over which was a network of iron. Some of them, it was stated, who wore double gloves of amianthus, held a red-hot bar during four minutes. Sir David Brewster, in his Letters on Natural Magic, page 305, gives a more detailed account of Aldini, from which the natural deduction is that the Chevalier was a showman with an intellect fully up to the demands of his art. Sir David says: In our own times the art of defending the hands and face, and indeed the whole body, from the action of heated iron and intense fire, has been applied to the nobler purpose of saving human life, and rescuing property from the flames. The revival and the improvement of this art we owe to the benevolence and the ingenuity of the Chevalier Aldini of Milan, who has travelled through all Europe to present this valuable gift to his species. Sir H. Davy had long ago shown that a safety lamp for illuminating mines, containing inflammable air, might be constructed of wire-gauze, alone, which prevented the flame within, however large or intense, from setting fire to the inflammable air without. This valuable property, which has been long in practical use, he ascribed to the conducting and radiating power of the wire-gauze, which carried off the heat of the flame, and deprived it of its power. The Chevalier Aldini conceived the idea of applying the same material, in combination with other badly conducting substances, as a protection against fire. The incombustible pieces of dress which he uses for the body, arms, and legs, are formed out of strong cloth, which has been steeped in a solution of alum, while those for the head, hands, and feet, are made of cloth of asbestos or amianthus. The head dress is a large cap which envelops the whole head down to the neck, having suitable perforations for the eyes, nose, and mouth. The stockings and cap are single, but the gloves are made of double amianthus cloth, to enable the fireman to take into his hand burning or red-hot bodies. The piece of ancient asbestos cloth preserved in the Vatican was formed, we believe, by mixing the asbestos with other fibrous substances; but M. Aldini has executed a piece of nearly the same size, 9 feet 5 inches long, and 5 feet 3 inches wide, which is much stronger